The present invention relates generally to powered fastener-driving tools, and particularly to trigger assemblies for such tools which operate between a sequential mode and a bottom trip or xe2x80x9cbump firexe2x80x9d mode. Power fastener-driving tools are typically powered electrically, pneumatically, by combustion or powder activated. The present invention is contemplated as being suitable with any such tool, suitable examples of which are sold under the PASLODE brand manufactured by Illinois Tool Works, Vernon Hills, Ill.
Power fastener-driving tools of the type used to drive nails, staples and other types of fasteners typically include a housing, a power source, a supply of fasteners, a trigger for operating the power mechanism and a workpiece contacting element. The latter component is typically reciprocally slidable relative to the housing and connected to the trigger mechanism in some way, so that the fastener will not be driven unless the tool is pressed against a workpiece. An example of such a prior fastener-driving tool is disclosed in U.S. Pat. No. 4,629,106, which is incorporated by reference.
Power fastener-driving tools, whether pneumatic, electric or combustion powered, typically have two operational modes. The operator may select the desired operational mode by moving a lever or actuating a latch or switch. In a first such mode, known as a sequential or single shot mode, depression or squeezing of the trigger will not initiate the driving of a fastener (xe2x80x9ca firingxe2x80x9d) without the workpiece contacting element being depressed in position against the workpiece. Similarly, upon the driving of the fastener, further depression of the trigger will not permit the driving of a subsequent fastener without the workpiece contacting element being in position. The sequential mode is typically employed in applications where greater care needs to be taken in driving each fastener, and the driving of multiple fasteners in a single location is to be avoided. Applications where the depth of the driven fastener is critical are typical environments in which the sequential mode is employed.
The other operational mode is termed bottom tripping or xe2x80x9cbump firingxe2x80x9d, and occurs where the operator holds the trigger in the depressed position, and the tool drives a fastener each time the workpiece contacting element is sufficiently depressed against the workpiece. In this mode, fastener driving occurs regardless of whether the trigger or the workpiece contact element is depressed first. Because the sequence described above in relation to the sequential mode need not be repeated for each fastener, the bottom tripping mode of operation is preferred when speed, not accuracy is needed to complete the job. Suitable examples of situations where bottom tripping is employed are rough residential framing and roofing, pallet construction or shipping crate construction.
One problem with conventional trigger assemblies for this type of tool is that the operator either cannot remember, or cannot easily tell by looking which tool mode has been selected. In the event the tool is in the bottom tripping mode, and the operator thinks it is in sequential mode, the result may be the inadvertent driving of a fastener into a workpiece, or even when the tool is bumped against another object during transport, since many operators carry the tools with the trigger depressed or squeezed.
A prior approach to this problem is disclosed in U.S. Pat. No. 6,116,488, incorporated by reference, which discloses a trigger assembly having a plate-like stop piece which pivots relative to the trigger and engages the workpiece contact element to provide a hard surface for depressing the control valve. To alternate between the sequential and bottom tripping modes, the pivot point of the stop piece is movable relative to the trigger. One problem of the assembly described in the ""488 patent is that when not engaged for driving a fastener, the stop piece moves freely relative to the trigger. Thus, in some cases, and especially when the tool is inverted or used on its side, the stop piece will not be in proper operational position. This is a significant drawback when the user needs to work overhead, as in ceiling construction.
Thus, a first object of the present invention is to provide an improved trigger assembly for a powered fastener tool in which the tool can be used when inverted.
Another object of the present invention is to provide an improved trigger assembly for a powered fastener-driving tool in which the mechanism for converting between sequential and bottom tripping modes is performed with a reduced number of components to reduce manufacturing and assembly costs.
Still another object of the present invention is to provide an improved trigger assembly for a powered fastener-driving tool in which the operator can readily select between the sequential and bottom tripping modes.
Yet another object of the present invention is to provide an improved trigger assembly for a powered fastener-driving tool which provides an indicator of whether the tool is in the sequential or bottom tripping modes.
The above-identified objects are met or exceeded by the present trigger assembly for use with powered fastener-driving tools, such as powered staplers and nail driving tools. To provide the capability of either sequential or bottom trip operation, the trigger assembly provides an actuator lever which is movable relative to the trigger between a sequential and a bottom trip position. A spring biases the lever against the trigger and holds it in place in the selected position, and also facilitates movement between the two positions.
More specifically, a trigger assembly is provided for a power fastener-driving tool having a housing, a control valve mounted to the tool and a reciprocating workpiece contacting element associated with the housing. The assembly includes a trigger member being pivotally engaged on the housing and having a pair of spaced walls, an actuation lever having a free end and a pivot end pivotally engaged on at least one of the walls, the free end being constructed and arranged for engaging the workpiece contacting element, and a biasing element for biasing the lever and the trigger away from the valve. At least one of the walls is configured for receiving the pivot end and for defining two positions for the lever, a first position which places the free end farther from the workpiece contacting element, and a second position which places the free end closer to the workpiece contacting element. The lever is selectively positionable in either the first position or the second position and is held in the selected position by the biasing element.